Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $125.27   7.505%   $134.6715   $134.67   $134.65   $134.70  
  Purchase #2 $46.77   11.351%   $52.0789   $52.08   $52.10   $52.10  
  Purchase #3 $238.34   5.461%   $251.3557   $251.36   $251.35   $251.40  
  Purchase #4 $238.88   7.654%   $257.1639   $257.16   $257.15   $257.20  
  Purchase #5 $95.93   11.568%   $107.0272   $107.03   $107.05   $107.00  
  Purchase #6 $60.76   3.867%   $63.1096   $63.11   $63.10   $63.10  
  Purchase #7 $230.77   3.508%   $238.8654   $238.87   $238.85   $238.90  
  7 purchase totals = $1,036.72       $1,104.2722   $1,104.28   $1,104.25   $1,104.40